1. Technical Field
The present invention relates to analog sensor circuits, and more particularly, to systems, devices, and methods of removing disturbance signals from analog differential sensor front end circuits using switched-capacitor topologies.
2. Background of the Invention
Differential switched-capacitor topologies are widely used in analog circuits. Correlate double sampling (CDS) techniques are oftentimes used in switched-capacitor circuits to reduce non-idealities of circuit components, such as amplifier offset and flicker noise, which can otherwise couple into the operational amplifier and cause large error signals. Typically, the CDS technique acts in two different phases: in the first phase the circuit measures an unwanted signal and stores it in a proper way; in the second phase the circuit removes the unwanted signal by way of subtraction in the path of the signal allowing the signal to pass through the circuit without the effect of the unwanted signal like, offset, and flicker noise (1/f).
Reducing unwanted quantities is of particular concern in applications using electronic sensors circuits that contain front end low-noise amplifiers. A major challenge exists in receiving read signals generated by a sensor while allowing as few circuit non-idealities as possible to enter the reading circuit. Sensors circuits that are part of portable, battery-operated systems place additional severe requirements regarding very low power consumption on front end circuits.
The two main sources of unwanted signals are offset and 1/f noise. It is possible to reduce both components by designing relatively large circuits; however, structures that occupy a large silicon area are disfavored mainly due to increased cost associated with such approaches. Particularly in the field of sensors, offsets can sometimes be relative large when compared to the sensor readout signal. A large offset signal has a strong impact on dynamic range and significantly limits the performance of the sensor read chain and, ultimately, the performance of the overall sensor reading system.
In order to increase efficiency of sensor systems, it would be desirable to have systems and methods that allow to read and store information associated with unwanted signal components and to remove such signals while reducing current consumption and optimizing dynamic range, thereby, improving overall circuit performance.